Answer:
It shows a 90° angle split into 2 separate angles so,
Basically, the total angle measure of the given angles [90°, (13 + x)°, and (4x + 2°) equals 180°. Take away 90 from 180 and you get 90, then solve for x using what's left: 13 + x + 4x + 2 = 90. You get x = 15.